p-diethylaminophenyl silanes



.in excess of 315 C.

United States Patent 3,340,286 p-DIETHYLAMINOPHENYL SILANES Harry M.Schiefer and Donald R. Weyenbel'g, Midland,

Mich., assignors to Dow Corning Corporation, Midland, Mich., acorporation of Michigan No Drawing. Original application Mar. 9, 1964,Ser. No.

350,543. Divided and this application Sept. 27, 1965, Ser. No. 506,141

Claims. (Cl. 260448.2)

' This application is a division of application Ser. No.

350,543, filed Mar. 9, 1964, which is a continuation-inpowerful engines,greater difficulty has been experienced in maintaining the stability ofthe lubricant under the higher temperatures encountered in theseengines. While many lubricants will work satisfactorily at a temperatureof 100 to 150 C., these lubricants at a temperature of 200 C. will forma large amount of sludge, increase in viscosity and become very acidic.This results in the corrosion of metals, particularly those beinglubricated, and

may result in the clogging of the lubricating system.

"Ihe 'best lubricants for jet engines have been found to be esters ofalkanoic acids and polyhydric alcohols which have at least two methylolgroups bonded to a quaternary carbon atom, such as1,2,2-trimethylolpropane. Even though these compounds have a high degreeof oxidative and heat stability, they are not stable in jet engines whenthe sump temperatures are in excess of 170 C. and the temperature atsome of the bearings is It is an object of the present invention toimprove the oxidative and heat stability of high temperature lubricatingfluids. In particular, it is an object to improve the oxidative and heatstability of the polyhydric alcohol ester lubricating fluids. Anotherobject is to provide high temperature lubricating fluids which areresistant to sludge formation.

These objects are obtained by a composition of matter mNO-nsnvh whereineach R is an alkyl radical of from 1 to inclusive carbon atoms, R is aradical selected from the group consisting of alkyl radicals of from 1to 10 inclusive carbon atoms, phenyl, vinyl, hydrogen atoms and .-OR"'radicals where R is an alkyl radical containing from 1 to 4 carbonatoms, R" is a radical selected from the group consisting of phenyl and-OR"' radicals where R'" is defined above and n is an integar of from 1.to 3 inclusive.

The antioxidant (2) is present in an amount from 0.1 to,5 percent byweight based upon the weight of the lubricating fluid. However, thepreferred range of the antioxidant is from 0.5 to 3 percent by Weight.There is generally very little improvement in the stability of thelubricating fluid when morethan 2 percent of the antioxidant is added. Rin the organosilicon antioxidant is an alkyl radical of from 1 to 10inclusive carbon atoms.

3,340,286 Patented Sept. 5, 1967 Examples of suitable R radicals aremethyl, ethyl, propyl, tert-butyl, octyl and decyl. R is an alkylradical of from 1 to 10 inclusive carbon atoms, phenyl, vinyl, hydrogenatoms or -OR"' radicals where R'" is an alkyl radical containing fromIto 4 carbon atoms. Since n is an integer of from 1 to 3 inclusive,there can be from 1 to 3 dialkylaminophenyl radicals per molecule. R" iseither a phenyl radical or an alkoxy radical, OR"', in which R is amonovalent alkyl radical containing from 1 to 4 carbon atoms, such asmethyl, ethyl, propyl, butyl or isopropyl radicals. R" is preferably aphenyl radical.

The antioxidants are prepared by first preparing a Grignard reagent andthen reacting this reagent with a chlorosilane. The first reaction isrepresented by the equation:

rim-G1: Mg RzNQ-MgX The new antioxidants of this invention are obtainedby reacting the above Grignard reagent with a chlorosilane in accordancewith the following equation:

R, R, R" and n are defined above. X is any halogen atom. Alternatively,these antioxidants can be prepared by first preparing a lithium reagentby the reaction of a p-halogeno-N,N-dialkylaniline with lithium. Thelithium reagent is then reacted with the proper chlorosilane.

Tetrahydrofuran is a suitable solvent for both reactions. Reaction 1 canbe conducted at a temperature slightly above room temperature. Reaction2 is best carried out at reflux for a substantial period of time. Theproduct can then be separated from the metal salts produced in reaction2.

Although all of the antioxidants disclosed above are useful, the bestantioxidants are those where R is ethyl, R is phenyl, R- is eitherphenyl or methyl, preferably phenyl and n is an integer of from 1 to 2inclusive. Examples of such compounds are The preferred antioxidant isThe antioxidants of the present invention besides providing anti-oxidantproperties and stabilizing the viscosity and the acidity of the hightemperature lubricating fluids, particularly theesters of alkanoicacids, also have an unexpected property of preventing sludge formationin the high temperature lubricating fluids. Antioxidants which containonly alkyl radicals attached to the silicon atom of the silane otherthan the dialkylaminophenyl radicals, do not prevent sludge formation.

Although these antioxidants are useful in stabilizing high temperatureorganic lubricating fluids in general, the

preferred lubricating fluids are esters of alkanoic acids and ofpolyhydric alcohols containing at least two methylol radicals bonded toa quaternary carbon atom, The

alkanoic acid must have at least 5 carbon 'atoms and preferably from 5to 8 carbon atoms. Although the straight-chained alkanoic acids arepreferred, the branched alkanic acids can also be used. Examples ofsuitable alkanoic acids are pentanoic, hexanoic, heptanoic and octanoicand 2,3-dimethylpentanoic acids. The polyhydric alcohols can also beesterified with a mixture of alkanoic acids.

The polyhydric alcohol contains at least two methylol groups on aquaternary carbon atom and can contain as many as four methylol groupson a quaternary carbon atom. The term quaternary carbon atom means thatthis carbon atom is bonded to four other carbon atoms. Thus, the carbonatom beta to the hydroxyl radical in these alcohols is not bonded to anyhydrogen atoms. Esters of such alcohols have a higher resistance tooxidation than those that have a hydrogen atom on the carbon atom whichis beta to the hydroxyl radical. Other examples of suitable polyhydricalcohols are 1,2,2-trimethylolpropane, 1,1,1-trimethylolethane,neopentylglycol, 2-butyl-2-ethy1- 1,3-propanedi ol, and2,2,4-trimethyl-l,3-pentanediol. The preferred ester is thetriheptanoate of trimethylolpropane.

These esters are prepared by the reaction of the polyhydric alcohol witha slight excess of alkanoic acid. Although it is not necessary to use acatalyst, a suitable catalyst, such as p-toluene sulfonic acid, benzenesulfonic acid, zinc and lead salts can be employed. This reaction ispreferably conducted at a temperature between 180 and 240 C. for aperiod between 6 and 14 hours. Water is eliminated by evaporation duringthe course of the reaction, preferably in the presence of an azeotropicagent, such as a fluid hydrocarbon.

Another type of suitable high temperature lubricating fluid are theesters of tert-alkylcarbinols and dicarboxylic acids. These carbin-olsalso have a methylol radical on a quaternary carbon atom. Hence, thereare no hydrogen atoms on the carbon atoms beta to the hydroxyl radical.Preferably the car-binol has from 5 to 12 inclusive carbon atoms.Examples of such carbinols are 2,2,4-trimethyll-pentanol, and1-methyl-cyclohexylmethanol. Preferably the dicarboxylic acid has from 4to 12 carbon atoms. Examples of suitable dicarboxylic acids areglutaric, adipic, suberic and sebacic acids. Sebacic and adipic acidsare preferred. Specific examples of such esters are bis(2, 2,4trimethylpentyl)sebacate, bis( 1 -methylcyclohexyl)- methyl)sebacate andbis(l methylcyclohexylmethyl) adipate. Methods for preparing theseesters are described in High-Temperature Lubricating Fluids, Blake,Edwards, Hammann, Reichard, Wright Air Development Command TR 54-532 Pt.2 (January 1956).

The antioxidants of this invention are used in the same manner in thesefluids as in the esters of alkanoic acids and polyhydric alcohols. Theheat and oxidative stability of these fluids are also increased when theantioxidants of this invention are added to them.

The oxidative and heat stability of mixtures of lubricating fluids isalso improved with the antioxidants of this invention. For example, theoxidative and heat stability of a mixture of a silicone lubricatingfluid and one of the previously described esters is improved by theantioxidants of this invention.

Applicants have also discovered that a mixture of one of thedialkylaminophenylsilane antioxidants and a conventional amineantioxidant prevents viscosity increase and acidification in hightemperature lubricating oils better than either of the compounds alone,even when the compounds are used in equivalent quantities. This is trueof both classes of the esters disclosed above. The preferred lubricatingfluids are the esters of polyhydric alcohols. Examples of some of theconventional antioxidants which can be used in combination with thepreviously described organosilicon antioxidants are;phenylu-naphthylamine, phenothiazine, phenyl-fi-naphthylamine,n-ethyl-l-naphthylamine, l-naphthylamine and dioctyldiphenylamine.Although a synergistic effect is obtained when any of these amines areused in combination with the organosilicon antioxidant, the best resultsare obtained with a combination of phenyl-u-naphthyla-mine and one ofthe organosilicon antioxidants previously described. For example, atriheptanoate of 1,2,2-trimethylolpropane which has been stabilized witha mixture of one percent phenyl-u-naphthylamine and one percent(p-diethylaminophenyl)triphenylsilane can resist a temperature of 218 C.for a period of time in excess of 30 hours. The synergistic effectobtained with these mixtures of antioxidants is believed to be due totheir complementary characteristics. It is belived that theorganosilicon cornpound functions at its best as an antioxidant at thehighest temperatures and that the organic amine provides the basicstability at lower temperatures. However, the applicants do not wish tobe bound by this particular theory. The mixture :of antioxidants is usedin the same range of weight limitations as set forth above for theorganosilicon antioxidant, i.e from 0.1 to 5 percent by weight basedupon the weight of the lubricating fluid. It is preferable that from 0.5to 3 percent by weight 'of the mixture be employed. The synergisticeffect obtained by this mixture is obtained when from 20 to percent byweight based on the weight of the antioxidant mixture is the organicamine and the remainder of the mixture is the organosilicon antioxidant.However, the best results are obtained when from 35 to 65 percent of themixture is the organic amine and the remainder is the organosiliconantioxidant.

Both the organosilicon antioxidant and/ or conventional antioxidants aremerely added to the high temperature lubricating fluid. In some cases itmay be desirable to heat the lubricating fluid in order to dissolve theantioxidant. When the mixture of antioxidants is used, they can be mixedtogether and the mixture added or they can be added separately to thelubricant.

The following examples are exemplary of the best method for thepreparation of the compounds of this invention. However, other methodscan be employed. In each case the reaction was carried out in a nitrogenatmosphere.

Example 1 50 ml. of tetrahydrofuran was added to a 500 ml. 3- neckedflask equipped with condenser, stirrer, and dropping funnel. 10 g.(0.412 g. atom) of magnesium turnings was then added. 68.0 g. (0.298mole) of p-bromo- N,N-diethylaniline was dissolved in 100 ml. oftetrahydrofuran. The reaction was primed twice by placing a few piecesof magnesium in a test tube with a few ml. of tetrahydrofuran andp-bromo-N,N-diethylaniline. Once the reaction had started in the testtube, the contents were dumped into the flask. Thep-bromo-N,N-diethylaniline in tetrahydro-furan was then added over aminute period. The pot temperature was 'maintained at about 30 to 40 C.during this time. The contents were then stirred for 45 minutes at roomtemperature. 51.2 g. (0.22 mole) of (C H (CH )SiCl was then dissolved in50 ml. of tetrahydrofuran and the solution was added to the reactionmixture over a 30 minute period. The pot temperature was maintained at30 to 35 C. during this time. The mixture was then refluxed for 7 hoursand then stirred at room temperature for 11 hours.

A solution of 42.72 g. of NH CI and 16 g. of NaOH in 800 ml. of H 0 wasprepared and placed in a beaker containing ice. The reaction mixturewas-poured into this solution. The organic layer was separated anddistilled at a reduced pressure of 0.20-0.22 mm. of Hg. 50.4 g. (65.4%yield) of a yellow liquid boiling at 202 to 208 C. was obtained. Theyellow liquid crystallized to give a tan solid with a melting point of68 to 70 C. The tan solid was recrystallized from ethanol and dried.40.3 g. of (p-diethylaminophenyl)diphenylmethylsilane, a white solidwith a melting point of 73 C., was obtained.

Example 2 The following organosilicon compounds were prepared inaccordance with the procedure of Example 1. Any modifications of theprocedure of Example 1 are set forth in the following paragraphs.

A. The compound (p-diethylaminophenyl)triphenylsilane was prepared bythe reaction of 68.43 g. (0.30 mole) p-bromo-N,N-diethylaniline with g.(0.41 g.- atom) of magnesium and 88.35 g. (0.30 mole) oftriphenylchlorosilane. The mixture was refluxed for 19 22.65 g. (41.9%yield of theoretical) of the pure prod-,

uct, bis (p-diethylaminophenyl)diphenylsilane.

C. The compound (p-diethylaminophenyl-phenyldimethylsilane was obtainedby the reaction of 68 g. (0.298 mole) of p-bromo-N,N-diethyl-anilinewith 10 g. (0.412 g.-atom) of magnesium turnings and 37.55 g. (0.22mole) of phenyldimethylchlorosilane. The mixture was refluxed for sevenand one-half hours and then hydrolyzed. The crude product was separatedby distillation at reduced pressure (0.25 to 0.36 mm./Hg).-Redistillation of the crude product at reduced pressure (0.1 mm./Hg)

' gave 32.2 g. (51.6% yield of theoretical) of the pure product,(p-diethylaminophenyl)phenyldimethylsilane.

D. The compound (p-diethylaminophenyl) diphenylvinylsilane was preparedby the reaction of 5.3 (0.22 gatom) magnesium turnings, 46.0 g. (0.22mole) diphenylvinylchlorosilane, and 45.6 g. (0.20 mole) p-bromo-N,N-diethylaniline. The diphenylvinylchlorosilane and the p-'bromo-N,N-diethylaniline was mixed with 50 ml. of"

tetrahydrofuran and added to a mixture of the magnesium and, 250 ml. oftetrahydrofuran over a two hour period. The temperature was maintainedat 45 C. during the addition and the material Was then refluxed for 45minutes. The product was hydrolyzed and recrystallized from ethanol andthen hexane. The melting point of the(pdiethylaminophenyl)diphenylvinylsilane was 67 to 70 C.

E. The compound (p-diethylaminophenyl)diphenylsilane was prepared byreacting 5.28 g. (0.22 mole) of magnesium turnings, 43.8 g. (0.20 mole)of diphenylchlorosilane and 47.9 g. (0.21 mole) of p-bromo-N,N-diethylaniline. The diphenylchlorosilane and the p-bromo-N,N-diethylaniline were mixed with ml. tet-rahydrofuran and added over atwo hour period to the magnesium mixed with 100 ml. of tetrahydroflrran.The temperature during this period was 45 C. and thematerial was thenrefluxed for one hour. The product Was hydrolyzed and recrystallizedfrom hexane. The melting point of (p-diethylaminophenyl)diphenylsilanewas 58 to 59 C.

F. The compound (p-diethylaminophenyl)methyldimethoxysilane was preparedby reacting 24.3 (1 g.-atom) of magnesium with 228 g. (2 moles) ofp-br-omo-N,N- diethylaniline. The Grignard product is then aded to 272g. (2 moles) of methyltrimethoxysilane over a 40 minute period. Thereactions were conducted in tetrahydrofuran. The temperature duringreaction was C. The tetrahydrofuran was stripped oif and the product Wasreplaced with toluene. The final product was distilled at 2 mm. of Hgand l25130 C. The (p-diethylaminophenyl) methyldimethoxysilane wasobtained in 39.4 yield.

Example 3 The antioxidant properties of the compounds'prepared in thepreceding examples when used alone or in combination withphenyl-a-naphthylamine in a lubricating fluid are measured in thefollowing tables. The lubricating fluid in which these antioxidantproperties were tested is the triheptanote of 1,2,2-trimethylolpropane.The antioxidant to be tested was merely added to the lubricating fluid.in the quantity set forth in the following tables. It was necessary insome cases to heat the antioxidant-containing lubricating fluid in orderto obtain a homogeneous solution.

In Table I, the stability of these lubricating fluids was tested byheating the fluid at 218 C. and then measuring the properties at theexpiration of certain time periods. Air was bubbled through thelubricating fluid at a rate of 8 liters of dry air per hour per 20 g. oflubricating fluid. The air was bubbled into the fluid through a ,5 in.

(inside diameter) tube. At the end of various time periods TABLE I Timein Vise. in Percent Increase Antioxidant hours cs. at Increase in AcidN0. in Acid 99 C. Viscosity Number (1) None 0 3.53 0.017 24 10. 05 18523. 1 23. 1 30 15. 28 333 25. 5 25.5 (2) 1% phenyl-a-naphthylamine 0 .3.60 0.014

24 5. 99 66. 4 18. 6 18. 6 30 7. 19 100. 0 19. 3 19. 3 (3) 2%phenyl-a-naphthylamine 0 3. 66 0.02

24 4.85 32. 5 7. 2 7. 2 (4) 1% (p-diethylaminophenyl)-triphenylsil- 0 3.52 0. l0 ane (Ex. 2A) and 1% phenyl-a-naphthyl- 22 3.72 6.7 0.39 0.3amine. 30 3. 68 4. 5 0. 45 0. 4 (5) 1%(p-diethylaminophenyl)methyldiphen- 0 3.65 0.10 ylsilane (Ex. 1) and 1%phenyl-a-naphthyl- 24 0.50 0.40 amine. (6) 0.5%bis(pdiethylaminophenyl)dlphenyl- 0 3.52 0.056 silane (Ex. 23) and 0.5%phenyl-a-naphthyl- 30 4. 74 35 12. 7 12. 6 amine.

The lubricating fluids tested in Table II were tested in the same manneras those tested in Table I except that the air was bubbled into thesample at a rate of 1 liter per hour per 20 g. sample. The viscosity andacid number were determined after 24 hours at 232 C. In Table II, thelubricating fluid without any additive had, prior to heating, aviscosity of 3.47 at 99 C. and an acid number of 0.28.

S F. dilheptanoate of neopentylglycol. G. bis 2,2,4-trimethylpentyl)sebacate. H. bis l-methylcyclohexylmethyl) sebacate. 1. bis(l-methylcyclo hexylmethyl) adipate.

Example 6 The heat and oxidative stability of tri heptanoate of1,2,2-trimethylolpropane lubricating fluid is increased TABLE II Vise.in cs. Percent Acid No. Additive at 99 C. Viscosity Acid No IncreaseIncrease (1) None 4.39 26.5 22.2 22.0 (2) 0.5% phenyl-a-naphthylarnine4.2 25.0 11.2 11.0 (3) 0.5% (p-diethylaminophenyl) triphenylsilane (Ex.2A) and. 0.5% 3.93 13.3 8.9 phenyl-a-naphthylamine. (4) 0.5%(p-diethylaminophenyl) tri- 3.82 10.1 2. 96

phenylsilane (Ex. 2A) and 0.5% phenyl-a-naphthylamine. (5) 0.5%(p-diethylaminophenyl)di- 4.17 18.1 19.6 19.1

phenylmethylsilane (Ex. 1). (6) 0.5% (p-diethylaminophenyl) rne- 4.1818.8 9.0

thyldiphenylsilane (Ex. 1) and 0.5% phenyl-a-naphthylamine. (7) 0.5%(p-diethylaminopheuyl) phen- 4.11 16.6 16.8 16.4

yldimethylsilane (Ex. (8) 0.5% (p-diethylaminophenyl)phen- 3.75 3.3 3.6

yldimethylsilane (Ex. 20) and 0.5% phenyl-a-naphthylamine.

Example 4 when any of the followlng comb1nat1ons of antioxidants Thefollowing products are obtained when the followweight of the lubricatingfluid, the oxidative and heat stability of the lubricating fluid isincreased.

are added to the fluid. All percentages are Weight percentages basedupon the weight of the lubricating fluid. A. 2.5 percentphenyl-a-naphthylamine and 2.5 percent bis(p-diethyl-aminophenyl)diphenylsilane.

B. 1.5 percent phenyl-B-naphthylamine and 1.5 percent(p-diethylaminophenyl triphenylsilane.

TABLE III Concen- Grignard Reagent Silane Product tration in lubricating(1) 0.30 111019 (C H11)2N -MgX 0.15 111019 (C6115) (CH2=CH)S1C11[(CaHn)gN-]3SKC5H6) (0151 0131) 1. 0 2 0.45 mole (O4Ha)1NMgX 0.15 molecorrosion o.H).N 3s1 ou1.) n. 5 (3) 0.30 mole (C3H ):NOMgX 0.15 mole(C5135) S1(OC3H7)3 [(C3H7)gN -]zSi(CaH5) (001117) 0. 2 (4) 0.15 mole(C5H11)zN- MgX 0.15 mole (CsHs) (CuH1a)1SiCI(CuIIuhN-O-SKCaHn)1(CtH5) 1. 5

(5) 0.15 mole (C1uH:1)2N- -MgX 0.15 mole (CuH5)n(C7H5)SiC1(OloHnhNQ-SKC5H5)g(CgH5) 2. 0

e 0.30 mole anew-Gm): 0.15 mole oH,=oH s1(0o,H5)a [(CzHbhN-QhSKOOgHb)(011F011 5. 0 7 0.15 mole (CzHshN-O-MgX 0.15 mole (OqHs)1(C1uHn)SiO1(CgH5)1N Sl(CaH5):(0101121) 0.8 (s) 0.30 mole (OzHs)zN MgX 0.15 mole(CoHa)(C4Hp)S1Ch Komem-O-nsuouao (0.11.) 2. 5

Example 5 Comparable results are obtained when any of the following hightemperature lubricating fluids are substituted for the triheptanoate of1,2,2-trimethylolpropane used in Example 3.

A. triheptanoate of 1,1,1-trimethylolethane.

B. tripentanoate of 1,2,2-t1imethylolpropane.

C. tetraheptanoate of pentacrythriotol.

D. diheptanoate of- Z-butyl-Z-ethyl-l,3-propylenediol. E. dioctanoate of2,2,4-trimethyl-1,3-pentanediol.

ethylarninophenyl) diphenylvinylsilane.

F. 1 percent dioctyldiphenylamine and 1 percent bis(pdipropylaminophenylpheny-lpropoxysilane.

Example 7 The oxidative and heat stability of a high temperaturelubricating fluid composed of 50 percent by weight of the in which n isan integer from 1 to 2 inclusive, at least one R is phenyl and anyremaining R groups are methyl radicals.

2. A silane of the formula 3. A silane of the formula (0:115) aN i(Caa)2( s) 10 4. A silane of the formula CBH5 3CHz)2NC S iR' (|]H=OH2wherein R is a radical selected from the group consisting of alkylradicals of from 1 to 10 inclusive carbon atoms, phenyl, vinyl, hydrogenatoms and -OR"' radicals where R is an 'alkyl radical containing from 1to 4 carbon atoms.

5. A silane of the formula References Cited UNITED STATES PATENTS1/1'957 McBride 260448.2

OTHER REFERENCES Gilman, H., et al.: Journal American Chemistry Society,vol. 73, pages 16861688, April 1951.

25 TOBIAS E. LEVOW, Primary Examiner.

J. G. LEVITT, P. F. SHAVER, Assistant Examiner.

1. A SILANE OF THE FORMULA 